DWiki now supports definition lists (<dl>, <dt>, <dd> in HTML). I
started with what I think was Wikipedia's syntax but decided it was
ugly in plain text so came up with my own that I like better.

A definition list looks like:

- <dt text>: <dd text starts here>
and can continue on as an indented list.

Definition lists nest, because it was trivial to make them do the
right thing this way; just add extra leading dashes. They nest with
both themselves and other types of lists, and the result validates.

Usage case: I started thinking about documenting the configuration
file format. This will have a lot of things like:

root

If present, this is taken as the root directory that further
configuration directives can specify relative paths from.

pagedir

The root directory of the page hierarchy.

tmpldir

The root directory of the template hierarchy.

I think this winds up looking all right, and better than the
alternative of somtehing like:

root: if present, this is the root directory for other
configuration directives to be relative to.

pagedir: the directory that is the root of the page hierarchy.

(Yeah, I definetly think that the first one is easier to read.)

The one drawback of this way of writing them is that they don't
entirely render in HTML the way they look in ASCII. However, this
looks better than the alternatives I've seen and thought about so
far.

(Yes, 'looks good in raw form' is one of ChrisSiebenmann's criteria
for DWikiText. Don't look so funny; it's important if we want
readable documentation, since we may spend a lot of time reading the
plain ASCII wikitext version. If it makes our eyes bleed and we can't
follow it cleanly, well...)